A typical optical communication system includes an optical transmitter that sends an optical signal and an optical receiver that receives the optical signal. In such an optical communication system, an optical signal is attenuated while traveling through a transmission path that connects the optical transmitter to the optical receiver. For the above, when the optical transmitter is started, the optical communication system controls the power of an optical signal to be sent from the optical transmitter such that the power of the optical signal when being received at the optical receiver is in a predetermined level. This control gradually increases the power of an optical signal from adequately small power in order to prevent an optical signal having power exceeding the maximum receivable power of the optical receiver from entering the optical receiver.
A mobile communication system increases, when a mobile device issues a connection request to a base station device, transmission electric power of a wireless signal by decreasing the number of subcarriers used for the wireless signal.
Another mobile communication system allocates common data to multiple subcarriers that are relatively low in communication quality to accomplish mobile communication.
[Patent Literature 1] Japanese Laid-open patent Publication No. 2005-136772
[Patent Literature 2] Japanese Laid-open patent Publication No. 2010-278684
[Patent Literature 3] WO2008/032381